Method of lifting a structure on the earth

ABSTRACT

A method of lifting a structure includes extending a pipe so as to have one end opening to a lens in the earth, connecting a pump to the pipe, and pumping a grout material through the pipe and into the lens so as to cause a strata of the earth above the lens to heave upwardly and to cause the structure to move upwardly. The grout is solidified in the lens. The pipe is removed after the step of pumping. The grout is a low mobility cement grout. A location of the lens nearest to the structure is determined prior to the step of extending the pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIALS SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to methods for lifting structures. More particularly, the present invention relates to methods for causing a heaving of the earth beneath the structure. More particularly, the present invention relates to methods of pumping grout into a lens in the earth for the purpose of heaving the strata of the earth located above the lens.

2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.

Subsidence is a problem that affects many areas around the world. Subsidence is a process whereby the surface of the layer eventually lowers because of a variety of reasons. More particularly, subsidence can occur whenever a lens or a seam in the earth becomes depleted so as to cause the strata of the earth located above the lens to lower toward the strata of earth located below the lens.

Whenever subsidence occurs, there can be extensive damage to buildings located on the surface of the earth in proximity to the subsidence. In many circumstances, homes and buildings are positioned on a surface of the earth that is subject to subsidence. As subsidence occurs, the structural integrity of the foundation of the building and the walls of the building become compromised because of pressures affecting such structures as a result of the subsidence. As a result, significant damage can occur to these structures.

The lens or seam in the earth typically retains a significant amount of groundwater. Conventionally, communities have tapped into this source of water for supplying water to the population located above the groundwater. As the groundwater becomes depleted, the seam or lens in the earth becomes depleted of the water. As a result, the material forming the lens is depleted and the strata of the earth located above the lens will sink so as to cause the subsidence.

Over a long period of time, the lens is formed in the earth as a result of the shifting of the earth and the geological activities affecting this portion of the earth. In particular, in coastal communities, there will be several lenses that are formed in various levels below the surface of the earth. Typically, a sand/silt lens will be formed as a result of water intrusion and water accumulation in such a lens. Typically, this sand/silt lens will have a clay formation located above the lens and a clay or rock formation formed below the lens. As a result, over time, groundwater becomes accumulated in the sand/silt lens and between the strata of the earth located above and below this sand/silt lens. As a result, it is desirable to supplement or to maintain the integrity of this sand/silt lens in order to reduce subsidence.

Many types of structures, such as residential homes, commercial buildings and industrial equipment, are erected on foundations that are, in turn, supported by unstable soil rather than a load-bearing formation, such as rock. These foundations are typically concrete slabs and may include a footing that is wider than the foundation to spread the load of the foundation and carried structure. Ultimately, the structural integrity and the level of the foundation and the carried structure are dependent on the stability of the underlying soil. Over time, the stability of the underlying soil may change. These changes may include shifting of the soil or subsidence of the underlying soil or portions of the supporting soil. Shifting of the soil may be caused by various geological and environmental conditions and/or the load carried by the structure. The changes in the supporting soil often result in damage to the structural integrity of the foundation and the carried structure and/or producing a non-level foundation. Left uncorrected, the settling of the soil and lack of stability of the foundation may result in loss of part or all of the value of the foundation and carried structure. Due to the frequency of damage to foundations from soil settlement, many systems have been attempted to stabilize the foundation and the correct positioning of the foundation.

The majority of methods and system utilized to correct foundation damage are costly and often only provide a temporary solution or an incomplete solution. Many of the prior art foundation repair systems consist of driving piers into the underlying soil until refusal of insertion is attained. It is desired that the piers be driven until bedrock is reached or until the frictional resistance to driving of the pier corresponds the compression of weight of the supported structure. Once the piers are positioned in the ground, hydraulic jacks are utilized to lift the foundation relative to the ground level. When the desired raised level is achieved, the pier is connected to the foundation to secure the foundation in place, at least for the short term. Another constant aspect of the prior art foundation lifting systems is the utilization of brackets, or supports, that connect to the underneath side of the foundation. This positioning of the brackets on the underside of the foundation requires that a portion of the underlying soil be excavated from beneath the foundation.

In various situations, it is necessary to raise and support the foundation within the perimeter of the foundation. Prior art methods and systems require cutting away a portion of the foundation and then excavating the soil from beneath the intact foundation to connect the lifting and supporting apparatus to the underside of the foundation. This additional excavation of the soil from beneath the intact foundation increases the time and cost of the project and increases the risk to workers as they position connections beneath the foundations.

The driving of piers, pilings or piles into the soil is a source of some of the most severe drawbacks of the prior art systems. Piers are typically driven into the ground utilizing a hydraulic mechanism until refusal and/or until the frictional resistance of the pier corresponds to the compression load of the foundation and structure. Very often bedrock is not encountered in the driven pier and is supported by an unstable foundation. It is also the case that the driven piers may pass through formations, such a shale or other tight soils, so as to increase the frictional resistance of driving the pier thereby providing misleading information as to the contact with a stable supporting foundation. These geological formations may only provide temporary lifting in support of the foundation. Over time, changes in soil moisture content and other geological conditions may result in reduced or increased skin friction of the soil/pier interface in these formations resulting in loss of stability from this formation.

Another problem with pier driving systems is maintaining a vertical alignment of the driven pier when the soil contains small boulders or other hard obstructions. As the pile is driven, it may encounter several different soil formations or other material that will cause the pier to deviate from vertical. Piers may be twisted and even turned so that a portion extends horizontal relative to the intended pier path. These occurrences make it appear as though the pier has encountered a load-bearing strata, such as bedrock. The result is an expensive temporary solution or even another source of foundation problems.

Additionally, the depletion of the sand/silt lens by utilization of groundwater, can further cause a lack of stability for these pier systems. In other words, the pier may extend to a location above the sand/silt lens. As the sand/silt lens becomes depleted and reduced in thickness, the supported pier will subside, along with the subsidence caused by the depletion of this layer. As a result, a need has developed so as to avoid the problems associated with such pier systems.

In the past, various patterns of issued relating to systems for lifting structures on the face of the earth. In particular, U.S. Pat. No. 4,673,315, issued on Jun. 16, 1987 to Shaw et al., describes an apparatus for raising and supporting a building. A lifting assembly is inserted underneath the foundation or slab and is adapted to receive a pipe assembly. A clamping assembly is provided for engaging a portion of the pipe assembly extending above the lifting assembly, and a hydraulic system extends between the lifting system and the clamping assembly for sequentially lowering the pipe assembly into the ground so that, when it encounters resistance, the foundation or slab is supported and can be raised to a predetermined level.

U.S. Pat. No. 4,765,777, issued on Aug. 23, 1988 to S. D. Gregory, shows an apparatus and method for raising and supporting a building. A lifting assembly engages a lower surface of the foundation or slab and is secured thereto. A piling is disposed adjacent the lifting assembly and is engaged by a driving assembly. A hydraulic ram is connected between the driving assembly and the lifting assembly in the expanded position of the ram so that when the ram is retracted, the piling is driven into the earth until it encounters a predetermined resistance. The ram is further actuated after the predetermined resistance is encountered to raise the foundation or slab a predetermined distance.

U.S. Pat. No. 4,787,779, issued on Nov. 29, 1988 to H. E. Clark, teaches an apparatus and method for raising and supporting a foundation in which a hole is excavated the beneath the foundation. One or more pipes are driven into the earth at diverging angles to form a piling. A jack is placed in the hole above the piling and beneath the foundation. A self-hardening fluid is forced into the jack to raise the foundation. A jack is created from a pair of hollow cylinders and slidably engaged for vertical movement when a self-hardening fluid is forced through an opening formed in one of the cylinders. The jack may be formed of an open-top cylinder having a concrete piston formed inside that is raised by pumping grout through an opening in the cylinder and into a void underneath the piston. U.S. Pat. No. 4,906,140, issued on Mar. 6, 1990 to H. E. Clark, shows a similar method and apparatus for raising and supporting a foundation.

U.S. Pat. No. 5,724,781, issued on Mar. 10, 1998 to Matthias et al., provides a method for raising foundations of building structures. This method uses a bracket assembly having a tubular portion with a central channel and a lip that extends from the tubular portion. The lip is placed under the bottom surface of the foundation or slab and an assembly of pilings is driven through the channel until bedrock or other similar load-bearing strata is encountered. A hydraulic cylinder having a ram is used to drive the sections of pipe. Once the bedrock is encountered by the pilings, a jacking saddle is attached to the bracket assembly in order to raise the foundation up a short distance in relation to the top of the piling. A gap is thus created between the slot in the bracket and the top of the uppermost pipe. A series of one or more pins is positioned in the gap in order to support the foundation upon the top of the piling and prevent the house from settling.

U.S. Pat. No. 5,951,206, issued on Sep. 14, 1999 to S. D. Gregory, shows a foundation lifting and support system in which two mounting units are attached underneath the foundation and to a wall of the foundation. A piling is inserted through support sleeves of the mounting units and a load is applied by a hydraulic unit to the pilings to drive the pilings to bedrock. After resistance is encountered, an additional load is applied to raise the foundation and the foundation is secured in the raised position.

U.S. Pat. No. 6,142,710, issued on Nov. 7, 2000 to Holland et al., provides an apparatus and method for raising a foundation which includes a lifting assembly for raising and supporting an edge of the foundation. A lifting saddle is slidably received over a pier that is driven into the ground adjacent the edge of the foundation. A bracket is supported by the lifting saddle and is adapted to be affixed to and to support the foundation. A load transfer device is configured to be supported atop an upper end of the pier. The lifting saddle is connected to the load transfer device by a threaded rod slidably received through the load transfer device. The bracket is pivotally connected to the lifting saddle such that the bracket can rock side-to-side so as to self-align and remain aligned with the foundation during a lifting operation. The bracket can also pivot about a vertical axis and can slide in a forward or rearward direction relative to the lifting saddle.

U.S. Pat. No. 6,193,442, issued on Feb. 27, 2001 to D. R. May, provides a lifting assembly for raising and supporting a foundation of a structure. The lifting assembly has a bracket that secures the base of the building foundation, a pier driven into the ground to a layer of bedrock, a pier support secured to the bracket to which the pier extends, and two shafts which secure a pier plate and a hydraulic plate to the pier support. The pier plate rests on the top end of the pier. A hydraulic jack is placed on top of the pier plate. The hydraulic plate is rigidly secured to the shafts whereby when the hydraulic jack is activated, the hydraulic jack is held in a fixed position by the hydraulic plate and forces the pier plate down downwardly so as to drive the pier into the ground.

U.S. Pat. No. 6,539,685, issued on Apr. 1, 2003 to Bell et al., provides an apparatus and method for lifting sunken foundations. This apparatus includes a lifting plate having a pipe section solidly secured thereto for passing concentrically over the anchor pier. The concentric lifting plate pipe precludes cocking or tilting of the plate relative to the anchor pier and foundation structured so as to greatly improve the security of the lifting operation. Only a single clamp is needed for securing the lifting assembly to the foundation. The clamp is adjustably positionable to secured to a solid area of the foundation structure. A plate is secured to the pier using mechanical fasteners so as to avoid the use of costly welding and other metal forming equipment.

U.S. Pat. No. 6,767,167, issued on Jul. 27, 2004 to D. A. Riales, shows a method and apparatus for lifting and stabilizing a foundation including a pier having a top end and a bottom end. The pier is disposed in a shaft that is drilled proximate the foundation to a desired underground formation suitable for supporting the foundation. A slab bracket is connected to a side of the foundation and not supporting the foundation from the underside thereof. A jacking bracket is attached to the top end of the pier and positioned below the slab bracket. A means is provided for supporting the foundation positioned between the jacking bracket and the slab bracket.

U.S. Pat. No. 7,278,802, issued on Oct. 9, 2007 to Bisson et al., teaches a device for raising and supporting the foundation of a building. This device includes a mobile assembly comprising facing jaws and an arm pivotable between a first position where an area between the facing jaws is open and a second position where this area is closed. An actuating means is adapted to draw the mobile assembly so as to drive a pile secured between the facing jaws when the arm is in the second position. The pile is made of a series of pile sections that are connected together. A pile section that needs to be added to the pile is front-loaded into position atop the pile and between the facing jaws when the arm is in the first position.

It is an object of the present invention to provide a method for lifting structures on the earth that maintains the integrity of the lens or seam in the earth.

It is another object of the present invention to provide a method of lifting a structure that effectively lifts the structure and the strata located above the lens or seam in the earth.

It is another object of the present invention to provide a method for lifting a structure that avoids the effects of groundwater depletion.

It is still another object of the present invention to provide a method of lifting a structure that elevates the structure without the need for piers or other supports.

It is another object of the present invention to provide a method of lifting a structure that is easy to use and relatively inexpensive.

It is still another object of the present invention to provide a method of lifting a structure that maintains the integrity of the structure and avoids the effects of subsidence upon the structure.

These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.

BRIEF SUMMARY OF THE INVENTION

The present invention is a method of lifting a structure which includes the steps of: (1) extending a pipe so as to have one end opening to a lens in the earth; (2) connected a pump to the pipe; and (3) pumping a grout material through the pipe and into the lens so as to cause a strata of the earth above the lens to heave upwardly and the cause the structure to move upwardly.

The grout material is solidified within the lens. The pipe is removed after the grout material is pumped into the lens. The grout material can be a particulate grout or a solution grout. In particular, the grout is a low mobility cement grout.

The present invention further includes the step of disconnecting at least one utility from the structure prior to the step of pumping. The location of the lens in the earth is determined prior to the step of extending the pipe. In particular, the lens is that lens which is nearest to the structure. The lens can be a sand/silt lens having a clay formation overlying the lens and a clay or rock formation underlying the lens.

The pump grout material is pumped to the pressure of between 50 and 150 p.s.i. The pipe can be a casing pipe or a drill stem.

The step of extending includes extending the pipe generally vertically through the earth to the lens. In particular, the step of extending comprises extending a plurality of pipes to the earth in spaced relation to each other. The grout material is sequentially pumped through the plurality of pipes to the lens.

This foregoing Section is intended to describe, with particularity, the preferred embodiment of the present invention. It is understood that modifications to this preferred embodiment can be made within the scope of the present claims. As such, this Section should not to be construed, in any way, as limiting of the broad scope of the present invention. The present invention should only be limited by the following claims and their legal equivalents.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an illustration showing the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is an illustration associated showing the method 10 of the present invention for lifting a structure 12 located on the surface 14 of the earth 16. In particular, the structure 12 can be a commercial building, a home, a facility, or other construction. Typically, the structure 12 will have a foundation 18 that is supported by the surface 14 of the earth 16. In particular, the surface 14 of the earth is likely to undergo subsidence or has encountered some subsidence.

The earth 16 includes a first strata 20, a lens or seam 22 and a second strata 24. In particular, the first strata 20 is a clay formation. This clay formation extends from the lens 22 to the surface 14. The clay formation formed in the first strata 20 overlies the lens 22. The second strata 24 is a clay or rock formation which underlies the lens 22. The strata formations shown in FIG. 1 would be typical of coastal regions.

Typically, the lens 22 is a seam in the earth located between the first strata 20 and the second strata 24. In particular, this lens 22 is a sand/silt lens which can contain groundwater therein. In normal use, as the groundwater is depleted by the communities located adjacent to this lens 22, the thickness of the lens 22 will be reduced so as to cause the first strata 22 subside. When this subsidence occurs, the foundation 18 and the structure 22 can be damaged, as was described hereinbefore. As such, in order to avoid this subsidence, it is important to enhance the integrity of the lens 22 and to maintain the thickness of such a lens.

In the method of the present invention, a pipe 26 is extended through the first strata 20 so as to have an end 28 opening to the lens 22. A suitable pump 30 can be connected to the pipe 26. The pump 30 will pump a grout material through the pipe 26 and into the lens 22 so as to cause the first strata 20 of the earth above the lens 22 to heave upwardly so as to cause the structure 12 to move upwardly.

The grout is a fluid form of concrete that is used to fill gaps. It is used in construction to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and sealed joints, such as though be those between tiles. Grout is generally a mixture of water, cement, sand and sometimes fine gravel. Unlike other structural pastes, such as plaster or joint compound, correctly-mixed and applied grout forms a waterproof seal. Grout is distinguishable from its close relative mortar by its viscosity. Grout is thin so that it flows readily into gaps, while mortar is thick enough to support not only its own way, but also that of the masonry placed on top of it.

Portland cement is the most common cementing agent in the grout, but urethane-and epoxy-based formulas are also popular. Portland cement-based grout come in different varieties depending on the particle size of the ground clinker used to make the compound, with a standard size of around 15μ, microfine at about 6-10μ, and ultrafine below 5μ. Finer particle sizes with the grout penetrate more deeply into a fissure.

In the present case, the grout material can be a particulate grout or a solution grout, such as polyurethane. In particular, the grout is a low mobility cement grout. As such, it will be generally contained within the area in which it is pumped.

The pipe 22 can be driven through the strata 20 of the earth so that the end 28 opens to the lens 22. In particular, the pipe 26 can be a casing pipe or a drill stem. If necessary, a hole can be first driven and the pipe inserted therethrough. In FIG. 1, the upper end 32 of the pipe 26 will be adjacent to the surface 14 of the earth. However, this is not critical to the function of the present invention. The upper end 32 can be below the surface 14 or can be above the surface 14. It is only important that the pump 30 be connected to the pipe 26 so that the grout can be delivered to the lens 22.

A supply of grout will be positioned on the surface 14. The pump 30 serves to transfer the grout from the supply into the pipe 26 and ultimately into the lens 22. The pump will deliver the grout at a pressure of between 50 and 150 p.s.i. However, the amount of pressure that is delivered will be dependent upon the weight of the structure 12. As such, if a very heavy structure 12 rests on the surface 14 of the earth, then it may be desirable deliver the grout with higher pressures. If the structure 12 is relatively small, such as a house, then a smaller amount of pressure will satisfy the requirements for the purposes of causing the strata 20 to heave. Also, the weight of the strata can also be important in determining the amount of pressure at which the grout is delivered into the lens 22.

Ultimately, when a desired amount of grout is delivered by the pipe 26 into the lens 22, the grout will solidify and cause the strata 12 to heave upwardly so as to cause the structure 12 to also move upwardly. The solidification of the grout will also create a permanent thickness of the lens 22 in the area of the structure 12. As such, this will to prevent any further subsidence caused by the depletion of groundwater from the lens 22. As such, this avoids the problem associated with piers, and other supporting structures, which do not maintain the structural integrity of the lens 22.

In order to properly lift the structure 12, it is first necessary to disconnect the various utilities from the structure 12. In particular, gas lines, water lines, and electrical lines are properly disconnected from the structure 12 prior to the step of pumping grout. As a result, any heaving of the strata 12 and the lifting of the structure 12 will not adversely affect the connections. After the structure 12 has been lifted by the process of the present invention, the utility lines can then be reconnected.

The location of the lens 22 should be that lens which is closest to the surface 14. Although it is possible to achieve the effect of the present invention by the delivery of grout to a lower lens, it is believed that the substantial benefits of the present invention are better achieved by introducing the grout into the lens closest to the surface 14 and closest to the structure 12. The location of the lens 22 can easily be determined by the drilling of a hole. As such, it is possible to establish the depth at which the end 28 should be moved through the strata 20 in order to allow the grout to be introduced into the lens 22. Seismic equipment can also be used so as to determine the location of the lens 22. Typically, in coastal areas, the sand/silt lens 22 will be approximately ten to twelve feet below the surface 14. However, in other circumstances, this lens may appear that a deeper location or a closer location.

To further cause the grout to maintain the structural integrity of the lens 22, a plurality of pipes 34, 36, 38 and 40 can also be used in spaced location so as to introduce the grout into the lens 22. Typically, the pipes 34, 36, 38 and 40 will be spaced by approximately twenty feet apart. As such, this creates injection points at various locations below the structure 12. The plurality of pipes 26, 34, 36, 38 and 40 further assures that the low mobility grout will only extend for a limited area. Also, the use of several pipes will further enhance the ability to cause heave in the first strata 20. The pumping of the grout will continue until the desired amount of heave is achieved. Each of the pipes 26, 34, 36, 38 and 40 extends generally vertically. However, it is possible within the concept of the present invention to actually use directional drilling in order to cause the grout to enter the lens 22.

After the desired amount of heave has been achieved in the first strata 20, the various pipes 26, 34, 36, 38 and 40 can then be removed and used in a different location. The grout will solidify so as to create a solid barrier between the strata 20 and strata 24 in order to maintain or enhance the thickness of the lens 22. The pump 30 can be sequentially used with the pipes 26, 34, 36, 38 and 40 in order to cause the grout material to flow through these pipes.

Since the present invention maintains the thickness of the lens 22, the amount of groundwater depletion will no longer adversely affect the structure 12. In other words, the grout will solidify so as to create a concrete barrier between the strata 20 and 24. If groundwater in locations away from the grouted-in the area occurs, it will not adversely affect the strata 20 nor result in further subsidence of the surface 14. Additionally, if there any piers or supports that underlie the structure 12, these piers or supports will heave with the heaving of the first strata 20 so as to continue to support the structure 12. As result, the present invention provides an effective technique for lifting the structure 12 to a desired elevation and to avoid the adverse effects of subsidence caused by the depletion of groundwater the reduction of the thickness of the lens 22.

It is contemplated that the method of the present invention can be utilized with seams other than the sand/silt lens. In certain circumstances, there are scenes are zones located between different strata of the earth. Even if the seam or zone does not contain the sand/silt lens, it can be utilized to receive the grout material for further avoiding subsidence.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents. 

I claim:
 1. A method of lifting a structure, the method comprising: extending the pipe so as to have one end opening to a lens in the earth; connecting a pump to said pipe; and pumping a grout material through said pipe and into said lens so as to cause a strata of the earth above the lens to heave upwardly and to cause the structure to move upwardly.
 2. The method of claim 1, further comprising: solidifying the grout material in the lens.
 3. The method of claim 1, further comprising: removing said pipe after the step of pumping.
 4. The method of claim 1, said grout material being a particulate grout or a solution grout.
 5. The method of claim 1, said grout material being a low mobility cement grout.
 6. The method of claim 1, further comprising: disconnecting a utility from the structure prior to the step of pumping.
 7. The method of claim 1, further comprising: determining a location of the lens in the earth nearest to the structure.
 8. The method of claim 7, the lens being a sand/silt lens having a clay formation overlying the lens and a clay or rock formation underlying the lens.
 9. The method of claim 1, the step of pumping comprising: pumping the grout material at a pressure of between 50 and 150 p.s.i.
 10. The method of claim 1, said pipe being a casing pipe or a drill stem.
 11. The method of claim 1, the step of extending comprising: extending said pipe generally vertically through the earth to the lens.
 12. The method of claim 1, the step of extending comprising: extending a plurality of pipes through the earth in spaced relation to each other, the step of pumping comprising pumping the grout material through said plurality of pipes to the lens.
 13. A method of lifting a structure that resides on the surface of the earth, the method comprising: determining a location of a lens in the earth; extending a pipe through the earth so as to have a lower end opening to the lens; and pumping a grout material through said pipe and into the lens so as to cause a strata of the earth above the lens to heave upwardly so as to cause the structure to move upwardly.
 14. The method of claim 13, further comprising: connecting a pump to the pipe so as to pump the grout material under pressure into the pipe.
 15. The method of claim 13, further comprising: solidifying the grout material in the lens.
 16. The method of claim 13, further comprising: removing said pipe after the step of pumping.
 17. The method of claim 13, said grout material being a low mobility cement grout.
 18. The method of claim 13, the lens being a sand/silt lens having a clay formation overlying the lens in a clay or rock formation underlying the lens.
 19. The method of claim 13, the step of pumping comprising: pumping the grout material at a pressure of between 50 and 150 p.s.i.
 20. The method of claim 13, the step of extending comprising: extending a plurality of pipes through the earth in spaced relation to each other, the step of pumping comprising pumping the grout material through said plurality of pipes to the lens. 